The right answer is B.
Cholera vaccination is only recommended for staff who have to intervene with patients in an epidemic situation. In all other cases, effective prevention is provided by good personal hygiene (washing hands) and food.
It is also important to know that this vaccine does not protect permanently: It protects only about 90% within 6 months, then to 50% within 3 years.
The snakehead could unreservedly eat little fish and scavangers, so that would evacuate/diminish the predator for zooplankton and phytoplankton. So zooplankton and phytoplankton populace would increment while little fish and scavanger populace would diminish. Presently if little fish and shellfish populace diminishes, their predators would have bring down sustenance, so vast fish pop. would diminish. On the off chance that vast fish pop. diminishes, their predators will have less nourishment thus the number of inhabitants in well evolved creatures will somewhat drop, however not by much, since they can feast upon zooplankton.
So at last, just the phytoplankton populace would increment while everything else diminishes.
